Large grassland area (7)
I believe the answer is:
prairie
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">large grassland area</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for prairie that I've seen before include "Extensive US grassland" , "Continental grassland of N America" , "Open grassland in the USA" , "this oyster produces an egg" , "Schooners once crossed it" .)